Insulating supporting roller in cathodic protection system

ABSTRACT

An underground gas main which is protected against electrolytic action by connection to a consumable or &#34;sacrificial&#34; anode of higher electric potential, is insulated from bridges or other grounded structures on which it is supported by supporting rollers of dielectric material which allow longitudinal movement but restrict lateral movement, and prevent passag of leakage current to ground.

Oct. 30, 1973 Original Filed Dec. 2 Sheets- Sheet 1 FIG. 3.

mvmwon CHARLES E. DEEM, JR.

BY g, 4M4

ATTORNEY c; E. DEEM, JR 3,769,190 INSULATING SUPPORTING ROLLER INCATHODIC PROTECTION SYSTEM 13, 1968 I Och 1973 c. E. DEEM, JR 3,769,19

INSULATING SUPPORTING ROLLER IN CATHODIC PROTECTION SYSTEM OriginalFiled Dec 13, 1968 2 Sheets-Shet 2 I0 42 I mvm'ron 6 CHARLES E. DEEM,JR.

ATTORNEY United States Patent INSULATING SUPPORTING ROLLER IN CATHODICPROTECTION SYSTEM Charles E. Deem, In, Line Lexington, Pa., assignor toUtility Products Co., Bala-Cynwyd, Pa. Continuation of abandonedapplication Ser. No. 783,660, Dec. 13,, 1968. This application June 4,1971, Ser.

Int. Cl. czar 13/00 Uls. c1. god-+191 1 Claim ABSTRACT OF THE DISCLOSUREAn underground gas main which is protected against electrolytic actionby'connection to a consumable or sacrificial anode of higher electricpotential, is insulated from bridges or other grounded structures onwhich it is supported "by supporting rollers of dielectric materialwhich allow longitudinal movement but restrict lateral movement, andprevent'passage of leakage current to ground. i

- the pipe is unaflected.

The protective current iskept to a minimum by substantially insulatingthe pipe from ground, but some leakage cannot be avoided. In passingover bridges and such metallic structures, the pipe is supported onrollers to provide for thermal expansion and contraction. These rollersare metal and are grounded through the metal structure so as .todirectly ground the pipe, resulting in excessive current drain on thesacrificial anode.

Various means to avoid this leakage current through bridges. and likestructures have been tried without success. Insulating bushings andwashers are ineffective. They may be broken downby highvoltage surges,such as caused by lightning. They are subject to leakage due todampness, or. snow and ice, and sometimes from carelessness in painting,and cannot be used on present-day bridge structures with metalcorrugated concrete forms.

Insulators in the supports to isolate the pipe from a bridge structurehave been used, but these are expensive and'impractical in many places.In modern bridge construction, the mains must be carried between thesupporting beams, where space is inadequate for insulators on thesupports.

The failure of these methods led to the practice of insulating theentire section of a gas main over a bridge from the protected pipe atopposite ends of the bridge. This-method isquite expensive and destroysthe electric continuity of the main, leaving the section over the bridgesubject-to corrosion.

Applicant avoids all these cumbersome and expensive and inadequateprotective methods by one simple change in'present,systemsusing'insulating supporting rollers en the supporting units to isolate thepipe electrically from the bridge structure. These insulating rollers,which may be made of any dielectric material having the necessarystrength to suppor'tthe pipe, are far less expensive than insulating thepipev section, and can be used with any type off pipe hanger where spacemay not allow the use of insulators. These rollers, may, also be appliedin structures now in use by merely substituting the insulating rollersfor the metal rollers.

The savings involved. in the use of insulating rollers over the presentpractice of insulating the pipe section over the bridge from the pipe atopposite ends are substantial. For example, on a typical installation ofan 8- inch pipe having a -foot span, the eight rollers required tosupport the pipe section would be on the order of onethird of the costof insulating the pipe section at its ends. At the same time, theelectrical continuity of the pipe is maintained and the section acrossthe bridge is adequately protected.

FIG. 1 shows a transverse section of a bridge with a gas main suspendedbelow the bridge deck.

FIG. 2 is a section taken on line 2-2 of FIG. 1.

FIG. 3 is a central transverse section of the roller, taken on line 33of FIG. 2.

FIG. 4 is a view similar to FIG. 2 showing another form of hangerstructure.

FIG. 5 is a perspective view of a roller and support for a pipe.

FIG. 6 is a sectional view showing a different type of bridge structurewith a modified form of pipe support.

FIGS. 1 to 3 show a pipe 1 supported on a bridge. In this construction,the concrete deck 2 is poured into and supported on a metal corrugatedform 3. The pipe is supported on the bridge by supporting unitsconnected to screw inserts 4, which are embedded in the concrete andrest on the corrugated form 3. Hanger rods 5 threaded in these screwinserts 4 carry blocks 6 on the lower ends adjustably held by nuts 7. Arod 8 extends between the blocks 6 and is seated in sockets 9.

A roller 10 is mounted for rotation on rod 9. The body of this roller 10is molded of a suitable dielectric material such as an epoxy resin mixedwith fiber glass, and with its periphery of channel shape curved toconform substantially to the curvature of the pipe. Various epoxy resinsmay be used. One example is a product sold under the name of Epi-Seal,called Spec. 10-40, manufactured by Bonded Products, Inc., of SouthOrange, NJ. The body of the roller is molded on the steel sleeve 11,which forms a bearing on rod 8 and also reinforces the roller. Therelative thickness of the central sleeve or metal portion and of thedielectric body is not critical, as long as the peripheral portion incontact with the pipe is of dielectric material, or dielectric materialis interposed between the pipe 1 and rod 8.

Longitudinal movement of the pipe may take place to allow for thermalexpansion and contraction, but any lateral movement is prevented by thecircumferential channel shape or curved saddle-shape of the body of theroller. The body of the roller is preferable longer than the diameter ofthe pipe to reduce the chance of contact with surrounding members. Withits substantial area of insulating material and its curved shape toprevent shifting of the pipe, this roller efiectively isolates the pipefrom the surrounding structure and the ground.

FIG. 4 shows an example of a hanger 20 in which the rods 21 are fastenedas in the hanger of FIG. 1, but carry springs 22 which rest on springseats 26 held by nuts 27. The same roller 10 may be supported on theblocks 26.

A stationary fixed base 30 is shown in FIG. 5, which may be bolted to asteel structure. A pin 32 rests in sockets in posts 31 on the base andcarries a roller 36 which may be similar to roller 10, or may differ inconfiguration as shown in FIG. 5, but which is substantiallycomplementary to the curvature of the pipe 1. p

A typical example of a bridge construction with the hanger structure andgas main is shown in FIG. 6. The bridge is constructed with pre-stressedconcrete box beams 42 on which are supported corrugated metal forms witha concrete deck. The pipe lies between the beams, so that short hangers40 are carried by the corrugated deck element 41, and the pipe may be aswide as said space except for the supporting element 5. The rollercarried by this hanger provides for isolating the pipe electrically,where the space is insuificient for insulators.

The several embodiments of the invention herein described andillustrated are only examples of many possible applications of theinvention, which is defined in the appended claim.

I claim:

1. In a fluid distribution pipe line in which a pipe passes through theearth and over a bridge having beams below its deck and is supportedbetween said beams by supporting units fixed to said bridge, each ofwhich has vertical metallic supporting elements between said beams onopposite sides of and spaced from said pipe, said pipe being protectedover said bridge against electrolytic decomposition by an anode ofhigher electric potential connected to said pipe and the earth, andbeing electrically continuous to assure protection throughout its lengthagainst electrolytic action, each supporting unit comprising a rod belowsaid pipe carried by said supporting elements and an insulating rollerrotatable on said rod on 4. which said pipe rests and is movablelongitudinally, said roller comprising a metal sleeve on said rod toform a bearing and a body of dielectric material having a peripheralportion of channel shape molded on said sleeve to insulate said pipefrom said supporting elements and bridge structure, said peripheralportion of said roller being longer than the diameter of the pipe toprevent contact of said pipe with said supporting elements and to spacesaid pipe from said supporting elements, so that a pipe may be carriedby the bridge between said beams of a dirneter only slightly less thanthe distancebetween said beams.

References Cited UNITED STATES PATENTS Newbury 248- TA-HSUNG TUNG,Primary Examiner

